In recent years, in wireless communications such as wideband code division multiple access (W-CDMA), improvement of transmission efficiency by digitization has been promoted. When multi-value phase modulation system is applied to wireless communications, a technology is used that linearizes the amplification characteristics of a power amplifier for transmission on the transmitting side and reduces nonlinear distortion, thereby reducing an adjacent channel leakage power.
For example, a known technology stores a plurality of distortion compensation coefficients used for distortion compensation in a look up table (LUT), and reads a distortion compensation coefficient from the LUT by designating an address according to the power value of a transmission signal. In addition, another known technology maintains distortion compensation performance in order to reduce memory effect in which the output of an amplifier at a certain time is affected by the past inputs due to an electrical transient response called an Idsq (drain current) drift in the amplifier.
For example, a known technology generates a second LUT address in addition to a first LUT address according to the power value of the current signal, and reads a distortion compensation coefficient from the LUT using the first LUT address and the second LUT address, the second LUT address being generated in consideration of a variation in the power value of the past signals (see, for example, Japanese Laid-open Patent Publication No. 2013-026631).